Dielectric composition containing a phenoxypropionitrile



Aug. 18, 1959 s. A. HEININGER .2,900,345

DIELECTRIC COMPOSITION CONTAINING A PHENOXYPROPIONITRILE Filed Feb. 24. 1954 United States Patent O P DIELECTRIC COB/[POSITION CONTAINING A PHENOXYPROPIONITRILE Samuel Allen Heininger, Dayton, Ohio, assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware Application February 24, 1954, Serial No. 412,225

7 Claims. (Cl. 252-63.'7)

The present invention relates to a method of insulating elements in electrical apparatus and conducting elements generally, and also to compositions therefor. specically the invention relates to the use of phenoxypropionitriles, particularly in electrical apparatus such as capacitors, transformers, circuit breakers, cables and the like containing the above composition.

It is an object of the present invention to provide new and improved methods of insulating elements and also to a dielectric composition therefor. A further object is the provision of liquids which are applicable in insulating electrical conductors in electrical equipment. Other objects will appear hereinafter.

The use of a dielectric is required in certain electrical equipment for the purpose of removing heat and of allowing the making of electrical contact in the absence of air or of explosive mixtures. The requirements for such dielectrics are, among other things, very high resistance to the ow of electric currents, high stability to atmospheric conditions at ordinary and at somewhat elevated temperatures, high resistance to thermal decomposition, low vapor pressure, low congealing temperature, low inflammability and high ash point. Preferably the dielectric should be a mobile liquid even at relatively low temperatures and should be a good heat transfer agent.

Iny commercial practice, high boiling fractions of petroleum distillates have been largely used for this purpose. These liquids do not satisfy all of the above-stated requirements. They are relatively poor heat transfer agents and under the conditions of their use they gradually decompose with the formation of undesirable products which adversely influence the electrical properties. Some of these products are tarry, and others are appreciably volatile and may present lire and explosion hazards.

Another disadvantage of the mineral oils is that they tend to form deposits generally known as sludge during the period of their use. This is due to oxidation and decomposition and also results to some extent in the formation of acids which is equally undesirable. The sludging of delectrics during use is a serious disadvantage and requires either replacement of the oil or treatment to remove the sludge and revivify the dielectric. A satisfactory dielectricY liquid should not sludge or undergo substantial deleterious changeiduring use and it is one of the objects of this invention to provide a liquid which does not possess this undesirable disadvantage characteristic of the mineral oils..

Halogenated organic compounds, more particularly halogenated aromatic compounds such as chlorinated biphenyl and chlorinated naphthalene are also highly useful electrical insulating materials because of their high dielectric constants, thermal stability, resistance to oxidation, non-arnmability and other valuable properties.

vHowever, it has been found that exposure to elevated temperatures and/or high voltages partially decomposes these compounds, thus liberating hydrogen halides which have an exceedingly deleterious action on the paper insulation and metal parts of electrical apparatus..

More- ICC For example, in transformers, circuit breakers and other electrical devices in which arcing occurs, the development of hydrogen halides as a result of the above decomposition presents a serious problem as they decrease the dielectric strength of the composition containing same and cause considerable damage by attaching paper insulation and corroding metal parts of the apparatus in which the composition is used. The undesirable effect of the above decomposition is `further manifested when the above halogenated organic compounds are used as capacitor impregnants. Thus, under high operating temperatures and direct current voltages, capacitors impregnated therewith undergo a characteristic type of deterioration which results in an ever increasing leakage current, a short capaitor life, visible localized decomposition of the dielectric and corrosion of the electrodes. Moreover, in the case of capacitors operating on alternating current, the decomposition sometimes results in an excessive increase in power factor of the dielectric material.

It is, therefore, an object of the present invention to provide a method for the insulation of elements in elecn trical apparatus wherein the above objectionable properties are either completely eliminated or substantially reduced.

An additional object is to provide transformers, capacitors, circuit breakers, cables and the like containing a phenoxypropionitrile, whereby the deleterious action common to the prior art dielectric materials such as the deterioration of paper insulation and metal parts is eliminated or materially reduced. In this Way, it is possible to operate such apparatus so as to have a longer, useful life and a greater dielectric stability than similar capacitors not containing the said phenoxypropionitriles.

Other objects and advantages of the present invention will become apparent to those skilled in the art as the description proceeds.

It has been discovered that the operation of electrical apparatus While insulating the elements thereof may be greatly improved by the use of phenoxypropionitriles interposed between the elements. Such compounds may be represented generically by the following general formula:

in which R is selected from the group consisting of hydrogen and alkyl radicals having from l to 18 carbon atoms and n is a whole number from l to 3. Illustrative examples of compounds of the present invention are phenoxypropionitrile, methyl phenoxypropionitrile (also known as cresoxy propionitrile), and the other alkyl-substituted phenoxypropionitriles in which the alkyl radical may be ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl and octadecyl radicals, which may be saturated or unsaturated and may also be straight chain or branched including cycloaliphatic radicals. The preparation of certain of the said phenoxypropionitriles is set forth in greater detail in copending application, Serial No. 412,063, led February 23, 1954, now abandoned.

For a more complete understanding of the present invention, reference is made to the accompanying drawings and the experimental data hereinafter presented in the specific examples.

Fig. l is a front elevation partly in section of a transformer; Fig. 2 illustrates a switch in a similar manner; Fig. 3 represents a rolled capacitor; Fig. 4 shows a sectional view of a portion of the electrodes and dielectric sheets of Fig. 3; and Fig. 5 is a side view of a cable, the casing being partly removed to permit the interior of the `parts to be seen.

The transformer illustrated in Fig. 1 comprises a casing 1, core 2, coils 3 insulated with manila paper, kraft paper, cotton or other iibrous insulation, insulating and cooling medium 4, lead-in busuhings 5, and suitable leads 6 connected to the coil assembly. The insulating and cooling medium may consist of a phenoxypropionitrile such as -nonyl phenoxypropionitrile which may be employed as such or in combination with a petroleum oil. These two components may be employed in any proportions, such as from 10% to 91% by weight of the phenoxypropionitrile. Other well-known liquid hydrocarbons or halogenated hydrocarbons or mixtures thereof may also be used in combination with the phenoxypropionitrile as the insulating and cooling liquid and various other halogenated organic compounds may constitute a part of such compositions, such as for example, halogenated compounds of naphthalene, toluene, benzene, nitrodiphenyl or diphenyl oxide. l

The switch shown in Fig. 2 comprises a casing 7, ixe contacts 8 and 9, and movable contacts 10 and 11 which cooperate therewith. The movable contacts are mounted upon a support 12 which in turn is operatively connected to actuating levers 13. A phenoxypropionitrile is illustrative of a suitable arc quenching liquid which may be used in this device, either as the sole dielectric, or in combination with a petroleum oil or a halogenated hydrocarbon as described above.

The capacitor shown in Fig. 3 is made up of alternate layers of metal foil such as aluminum or tin foil separated by sheets of dielectric material. It is produced by interleaving two dielectric sheets, such as linen or kraft paper, with the metal foil, and rolling the interleaved sheets in the conventional manner. The rolled capacitor is then impregnated with the dielectric composition by any suitable process, such as vacuum impregnation with a phenoxypropionitrile. The capacitor is then placed in a protective case or otherwise used as desired. Fig. 4 shows a section of one turn of the nished rolled capacitor iilustrating the alternate electrodes and dielectric layers. In accordance with the present invention, the finished capacitor contains a phenoxypropionitrile.

The cable of Fig. comprises a core 14, cable conductors 15, insulation consisting of paper or other suitable material 16 and a casing 17. The space between the insulated conductors and the casing is filled with a phenoxypropionitrile or with a mixture of the same with a hydrocarbon or a liquid chlorinated organic compound as described above.

The experimental data hereinafter presented illustrates in a striking manner the dielectric properties of the above dielectric composition and the improvement possible in insulating elements in electrical apparatus therewith.

The following table illustrates the electrical properties of beta-nonylphenoxypropionitrile and beta-phenoxypropionitrile.

100 kc., 25 C. 100 kc., 100 C.

Resis- Compound tivity,

Dielectric Power Dielectric Power u constant factor, constant factor, ohm-em percent percent B-nonylphenoxypropionitrile 10. 88 0. 54 8. 26 7. l 520 B-phenoxypropionitrile 3 7. 8 21,000

nitriles may also be employed in combination with another dielectric liquid, such as a hydrocarbon or chlorinated biphenyl, trichlorobenzene, chlorinated naphthalene, chlorinated diphenyl ketone, chlorinated diphenyl oxide, chlorinated diphenyl methane, chlorinated diphenyl ethane, chlorinated benzene, chlorinated toluene, chlorinated nitrodiphenyl, chlorinated alkylated benzenes, chlorinated alkylated biphenyl, ethyl trichlorobenzene, ethyl tetrachlorobenzene, ethyl pentachlorobenzene, chlorinated terphenyls, chlorinated quaterphenyls, chlorinated parafiinic hydrocarbons, chlorinated alicyclic hydrocarbons, chlorinated oxygen-containing organic compounds, chlorinated rubber, chlorobutadiene polymers, chlorinated fats, chlorinated vegetable oils, chlorinated animal oils, chlorinated mineral oils or mixtures of one or more of these. In such mixtures and phenoxypropionitrile may be employed in all proportions with the additional dielectric component.

What is claimed is:

1. An electrical insulating composition comprising from 9% to 90% by weight of a petroleum oil in combination with from 10% to 91% by weight of a phenoxypropionitrile lIlOlIl in which R is selected from the group consisting of hydrogen and alkyl radicals having from 1 to 18 carbon atoms, and n is a whole number from 1 to 3.

3. An electrical insulating composition comprising from 9% to 90% by weight of a petroleum oil in combination with from 10% to 91% by weight of -nonylphenoxypropionitrile.

4. An electrical insulating composition comprising from 9% to 90% by weight of a petroleum oil in combination with from 10% to 91% by weight of a phenoxypropionitrile substituted by an alkyl radical having from 1 to 18 carbon atoms.

5. A dielectric composition comprising from 9% to by weight of a petroleum oil in combination with from 10% to 91% by Weight of phenoxypropionitrile.

6. A dielectric composition comprising from 9% to 90% by weight of a petroleum oil in combination with from 10% to 91% by weight of -nonylphenoxypropionitrile.

7. A dielectric composition comprising from 9% to 90% by weight of a petroleum oil in combination with from 10% to 91% by weight of a phenoxypropionitrile substituted by an alkyl radical having from 1 to 18 carbon atoms.

References Cited in the iile of this patent UNITED STATES PATENTS 1,856,186 Hofmann et al May 3, 1932 1,994,911 Ford Mar. 19, 1935 2,041,594 Clark May 19, 1936 2,143,685 Clark Jan. l0, 1939 2,377,689 Hyde lune 5, 1945 2,407,493 Hart Sept. 10, 1946 2,445,563 Clark July 20, 1948 2,450,650 Flowers Oct. 5, 1948 2,682,024 Kohman June 22, 1954 

